With polls indicating a third-party candidate could have an impact on the U.S. Senate race in North Carolina between Democratic Sen. Kay Hagan and Republican Thom Tillis, the U.S. Chamber of Commerce has released a new ad featuring Sen. Rand Paul of Kentucky.

But Republicans are now hopeful Mr. Paul’s libertarian bona fides can boost Mr. Tillis in a race where Libertarian candidate Sean Haugh is polling in the single digits, but could still influence the outcome if the contest remains close.